This invention is generally concerned with thermal printing apparatus for processing letters and more particularly with thermal printing apparatus including structure for perforating postage indicia images on used thermal transfer ribbons.
For marking letters, including letter mail, thermal transfer printing offers an advantage over die cast image transfer processes, in that images transferred by means of thermal transfer printing processes exhibit higher quality image resolution than other printing processes. In such processes, the postage indicia images remaining on the ribbon after transferring therefrom an ink pattern corresponding to postage indicia, is ordinarily directly or indirectly wound on a take-up spool. In this connection, reference is made to U.S. patent application Ser. N0. 000,584, now cont. Ser. No. 251013 of Danilo P. Buan, Albert C. Chiang and Donald T. Dolan for a Thermal Transfer Printing Apparatus And Method, filed Jan. 6, 1987 and assigned to the assignee of the present invention.
In the aforesaid patent application, a two-step thermal transfer printing process is disclosed wherein the ribbon from the supply spool is passed through a first printing station, at which an outline of indicia pattern of the postage indicia which is to be printed on a letter is removed from the ribbon, then passed through a second station at which the remaining postage indicia pattern is printed on the letter, thereby removing all ink from the ribbon and providing a "blank" ribbon, and then passed back through the first printing station where the outline of indicia pattern is printed on the blank ribbon before the ribbon is wound on the take-up spool. The ribbon wound on the take-up spool thus bears a series of images of postage indicia outlines, including the outline of the postage value included in the postage indicia printed on the letter. Since the indicia outlines, if printed on a letter, might escape detection (as unacceptable) by mechanized postage handling equipment used by Postal Services, there is a need to provide more security against fraudulent use of the used ribbon in thermal printing apparatus adapted for printing postage, and other monetary values.
Accordingly:
An object of the invention is to provide improved thermal printing methods and apparatus;
Another object is to provide an improved thermal transfer ribbon cartridge;
Another object to provide thermal printing apparatus including a method and apparatus for preventing the re-use of used thermal transfer ribbon;
Another object is to provide a thermal transfer ribbon cartridge including means for preventing the re-use of used thermal transfer ribbon; and
Another object is to provide a method and apparatus for perforating or otherwise destroying postage value indicia patterns on used thermal transfer ribbon.